1. Field of the Invention
The present invention relates to a thermal processing apparatus and, more particularly, to a thermal processing apparatus for applying a thermal process to a substrate such as a single crystal silicon substrate or a glass substrate.
The present invention is especially suitable for a rapid thermal processing (RTP) apparatus, which is preferably used for a manufacturing process of semiconductor devices such as a memory device or an integrated circuit (IC). The RTP includes a rapid thermal annealing (RTA), a rapid thermal cleaning (RTC), a rapid thermal chemical vapor deposition (RTCVD), a rapid thermal oxidation (RTO), a rapid thermal nitriding (RTN), etc.
2. Description of the Related Art
Generally, in a manufacturing process of a semiconductor integrated circuit, a semiconductor substrate such as a silicon wafer is repeatedly subject to various thermal processes or heat treatment processes. The thermal processes may include a film deposition process, an annealing process, an oxidation diffusion process, a sputtering process, an etching process, a nitriding process, etc.
In order to improve a yield rate and a quality of semiconductor products, the RTP technique, which rapidly increases and decreases a temperature of an object to be processed, has attracted a great attention. A conventional RTP apparatus generally comprises: a single-wafer process chamber in which an object to be processed, such as a semiconductor wafer, a glass substrate for photo-masking, a glass substrate for liquid-crystal display or a substrate for an optical disk, is placed; a quartz-glass window attached to the process chamber; a heating lamp such as a halogen lamp; and a reflector provided on an opposite side of the object to be processed with respect to the heating lamp. Hereinafter, the object to be processed may be referred to as a target object.
The quartz-glass window is formed in a plate-like shape or in a tubular shape in which the target object can be accommodated. When gas inside the process chamber is evacuated by a vacuum pump and a negative pressure environment is maintained in the process chamber, the quartz window has a thickness of about 30 mm to 40 mm so as to withstand with a pressure difference between inside the process chamber and an atmospheric pressure. The quartz-glass window may have a concave shape so that the center thereof is apart from the process space inside the process chamber since the quartz window tends to be bent toward the processing space due to a temperature increase.
A plurality of halogen lamps are arranged so as to evenly heat the target object, and the reflector uniformly reflects an infrared light toward the target object. The process chamber is typically provided with a gate valve on a sidewall thereof so as to let the target object transported therethrough. Additionally, a gas supply nozzle is connected to the sidewall of the process chamber so as to introduce a process gas used for a thermal processing.
Since the temperature of the target object influences a quality of the process (for example, a thickness of a deposited film in a film deposition process), the temperature must be accurately detected. In order to achieve a rapid temperature increase or decrease, a temperature-measuring device is provided in the process chamber so as to measure the temperature of the target object. The temperature-measuring device may be comprised of a thermocouple. However, the thermocouple may contaminate the target object due to a metal constituting the thermocouple since the thermocouple must be brought into contact with the target object.
Accordingly, a pyrometer has been suggested, such as disclosed in Japanese Laid-Open Patent Application No. 11-258051, as a temperature-measuring device for measuring a temperature of the target object. The pyrometer calculates a temperature of the target object by converting an emissivity xcex5 into a temperature, the emissivity xcex5 being calculated by the following equation (1) based on an intensity of radiation of infrared light radiated from a back surface of the target object.
Em(T)=xcex5EBB(T)xe2x80x83xe2x80x83(1) 
In equation (1), EBB (T) represents an intensity of radiation from a black body having a temperature T, Em(T) represents an intensity of radiation from a target object, and e represents an emissivity of the target object.
In operation, the target object is introduced into the process chamber through the gate valve, and supported by a holder on its periphery. During a thermal process, a process gas such as nitrogen or oxygen is introduced into the process chamber through gas supply nozzles. On the other hand, the target object absorbs an infrared light radiated by the halogen lamp, thereby increasing the temperature of the target object. An output of the halogen lamp is feedback-controlled in accordance with a result of measurement of the temperature-measuring device.
In the conventional RTP apparatus, the target object is heated from both sides or a single side thereof. However, it is difficult to achieve both a rapid heating and a rapid cooling with a low-power consumption. That is, it is difficult to achieve a rapid cooling in an arrangement to heat both sides of the target object since such an arrangement can achieve a rapid heating at a low-power consumption but has a small heat releasing efficiency. On the other hand, an arrangement to heat a single side of the target object, such as an arrangement disclosed in Japanese Laid-Open Patent Application No. 11-258051, has a relatively high cooling rate since a cooled plate is arranged on a side opposite to the heating side. However, this arrangement requires a large-power consumption since an amount of heat released during the heating process is increased.
It is a general object of the present invention to provide an improved and useful thermal processing apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a thermal processing apparatus, which can rapidly increase and decrease a temperature of a target object at a low-power consumption.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a thermal processing apparatus for processing an object to be processed, the object having a first surface and a second surface opposite to the first surface, the thermal processing apparatus comprising: a process chamber in which the object is subject to a thermal treatment; a heat source heating the object from a side of the first surface; a cooling arrangement cooling the object from a side of the second surface, a distance between the cooling arrangement and the second surface of the object being equal to or less than a predetermined distance; and introducing means for introducing a gas having a predetermined thermal conductivity into a space between the object and the cooling arrangement so as to promote heat transfer from the object to the cooling arrangement.
According to the above-mentioned invention, the gas having high thermal conductivity can be introduced between the object to be processed and the cooling arrangement after the heat treatment is completed. The distance between the object to be processed and the cooling arrangement is set to the predetermined short distance. Thus, transfer of heat from the object to the cooling arrangement is promoted by the combination of the gas between the object and the cooling arrangement and the short distance between the cooling arrangement and the object.
In one embodiment of the present invention, the introducing means may introduce helium or hydrogen into the space between the object and the cooling arrangement, and the predetermined distance may be equal to or less than 5 mm. Additionally, the thermal processing apparatus according to the present invention may further comprise a moving mechanism, which moves at least one of the object and the cooling arrangement relative to each other. Further, the introducing means may include a shower plate facing the second surface of the object. The shower plate may be formed in a bottom part of the process chamber.
Additionally, there is provided according another aspect of the present invention a thermal processing apparatus for processing an object to be processed, the object having a first surface and a second surface opposite to the first surface, the thermal processing apparatus comprising: a process chamber in which the object is subject to a thermal treatment; a heat source heating the object from a side of the first surface; a cooling arrangement cooling the object from a side of the second surface; and a moving mechanism moving at least one of the object and the cooling arrangement relative to each other so that a distance between the cooling arrangement and said second surface of said object is set to be equal to or less than a predetermined distance.
According to the above-mentioned invention, the cooling arrangement can be moved away from the object when the object is subjected to the heat treatment. On the other hand, the cooling arrangement can be moved close to the object when the object is cooled. Thus, the object can be heated with less influence by the cooling arrangement while the object can be efficiently cooled by the cooling arrangement being moved close to the object.
In one embodiment of the present invention, the cooling arrangement may include a bottom part of the process chamber, the bottom part being cooled and facing the second surface of the object so as to cool the object, the predetermined distance being measured as a distance between the second surface of the object and the bottom part. Additionally, the bottom part may be movable relative to the object by the moving mechanism.
Additionally, there is provided according to another aspect of the present invention a thermal processing method for applying a thermal treatment to an object to be processed, the object having a first surface and a second surface opposite to the first surface, the thermal processing method comprising the steps of: heating the first surface of the object by a heat source so as to apply the thermal treatment to the object; after completion of the thermal treatment, cooling the second surface of the object by a cooling arrangement positioned on a side of the second surface with respect to the object by setting a distance between the object and the cooling arrangement to a value equal to or less than 5 mm; and introducing a gas into a space between the object and the cooling arrangement so as to promote heat transfer between the object and the cooling arrangement.
The introducing step may include a step of introducing helium or hydrogen into the space between the object and the cooling arrangement. The thermal processing method may further comprise a step of moving at least one of the object and the cooling arrangement relative to each other after completion of the heating step.
Additionally, there is provided according to another aspect of the present invention a thermal processing method for applying a thermal treatment to an object to be processed, the object having a first surface and a second surface opposite to the first surface, the thermal processing method comprising the steps of: heating the first surface of the object by a heat source so as to apply the thermal treatment to the object; after completion of the thermal treatment, moving at least one of the object and a bottom part of the process chamber so as to set a distance between the object and the bottom part to a predetermined distance, a distance between the object and the bottom part, the bottom part facing the second surface of the object; and cooling the object by cooling the bottom part of the process chamber.
Additionally, there is provided according to another aspect of the present invention a thermal processing method for applying a thermal treatment to an object to be processed, the object having a first surface and a second surface opposite to the first surface, the thermal processing method comprising the steps of: moving at least one of the object and a bottom part of a process chamber in which the object is subjected to the thermal treatment so that the second surface of the object is separated from the bottom part of the process chamber by a first distance, the bottom part facing the second surface of the object; heating the first surface of the object by a heat source so as to apply the thermal treatment to the object, the heat source being arranged on a side of the first surface with respect to the object; after completion of the thermal treatment, moving at least one of the object and the bottom part so as to change the first distance to a second distance smaller than the first distance; and cooling the object by cooling the bottom part of the process chamber.
The thermal processing method may further comprise a step of introducing a gas into a space between the object and the bottom part so as to promote heat transfer between the object and the bottom part of the process chamber. The introducing step may include a step of introducing helium or hydrogen into a space between the object and the bottom part of the process chamber.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.